Transflective liquid crystal display device with barrier metal layer between ohmic-contact layer and source/drain electrode patterns and fabrication method thereof

ABSTRACT

A trans-reflective LCD and a manufacturing method thereof are provided to simplify a manufacturing process and improve yield by reducing the number of masks and implement high definition by preventing wavy noise. A first substrate divided into a pixel unit and first and second pad units is provided. Through a first mask process, a gate electrode and a gate line are formed in the pixel unit of the first substrate. Through a second mask process, an active pattern of an island type is formed on the gate electrode in a state when a first insulating layer is interposed. On the active pattern, an n+ amorphous silicon thin film pattern and a conductive layer pattern are formed. Through a third mask process, a source electrode and a drain electrode are formed in the pixel unit of the first substrate. A data line crosses the gate line to define a pixel area comprising a reflection unit and a transmission unit. Through the third mask process, a pixel electrode comprising a transparent conductive layer is formed in the transmission unit of the pixel area. Through a fourth mask process, a second insulating layer is formed on the first substrate. Through a fifth process, a reflection electrode comprising an opaque conductive layer is formed in the reflection unit of the pixel area. The first substrate is deposited with a second substrate.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. 119 and 35U.S.C. 365 to Korean Patent Application No. 10-2006-0134202 filed onDec. 26, 2006, which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a display device and,more particularly, to a transflective liquid crystal display (LCD)device and a fabrication method thereof. Although embodiments ofinvention are suitable for a wide scope of applications, it isparticularly suitable for simplifying a fabrication process andimproving production yield by reducing the number of masks and alsosuitable for implementing high picture quality by preventing generationof wavy noise.

2. Description of the Related Art

As the consumer's interest in information displays is growing and thedemand for portable (mobile) information devices is increasing, researchand commercialization of light and thin flat panel displays (“FPD”) hasincreased.

Among FPDs, the liquid crystal display (“LCD”) is a device fordisplaying images by using optical anisotropy of liquid crystal. LCDdevices exhibit excellent resolution and color and picture quality, soit is widely used for notebook computers or desktop monitors, and thelike.

The LCD includes a color filter substrate, an array substrate and aliquid crystal layer formed between the color filter substrate and thearray substrate.

An active matrix (AM) driving method commonly used for the LCD is amethod in which liquid crystal molecules in a pixel part are driven byusing amorphous silicon thin film transistors (a-Si TFTs) as switchingelements.

In the fabricating process of the LCD, a plurality of masking processes(namely, photographing processes) are performed to fabricate the arraysubstrate including the TFTs, so a method for reducing the number ofmasking process will increase productivity.

The general structure of the LCD will now be described in detail withreference to FIG. 1.

FIG. 1 is an exploded perspective view showing a general LCD.

As shown in FIG. 1, the LCD includes a color filter substrate 5, anarray substrate 10 and a liquid crystal layer 30 formed between thecolor filter substrate 5 and the array substrate 10.

The color filter substrate 5 includes a color filter (C) including aplurality of sub-color filters 7 that implement red, green and bluecolors, a black matrix 6 for dividing the sub-color filters 7 andblocking light transmission through the liquid crystal layer 30, and atransparent common electrode 8 for applying voltage to the liquidcrystal layer 30.

The array substrate 10 includes gate lines 16 and data lines 17 whichare arranged vertically and horizontally to define a plurality of pixelregions (P), TFTs, switching elements, formed at respective crossings ofthe gate lines 16 and the data lines 17, and pixel electrodes 18 formedon the pixel regions (P).

The color filter substrate 5 and the array substrate 10 are attached ina facing manner by a sealant (not shown) formed at an edge of an imagedisplay region to form a liquid crystal panel, and the attachment of thecolor filter substrates 5 and the array substrate 10 is made by anattachment key formed on the color filter substrate 5 or the arraysubstrate 10.

The general LCD expresses an image by light emitted from a light sourcesuch as a backlight positioned at a lower portion of a liquid crystalpanel. However, the actual amount of light transmitted through theliquid crystal panel is about 7% of the light generated by thebacklight, causing severe loss of light, so power consumption by thebacklight is high.

Recently, to solve the problem of the high power consumption, areflective LCD that does not use such a backlight has been studied. Thetransflective LCD uses natural light as a means for expressing an image,without such power consumption caused by the backlight, so it can beused in a carried-around state for a long time.

Unlike an existing transmissive LCD, the reflective LCD uses an opaquematerial having reflectivity characteristics at a pixel region toreflect light made incident from an external source to thus express animage.

However, because natural or an artificial light source does not existalways, the reflective LCD can be used during day time when naturallight is present or in an office or in a building where an externalartificial optical source is provided. Namely, the reflective LCD cannotbe used in a dark environment in which natural light is not present.

To solve the problem, a transflective LCD, which combines the advantagesof the reflective LCD using natural light and the transmissive LCD thatuses a backlight, is being actively studied. The transflective LCD canbe changed to a reflective mode and a transmissive mode according to auser intention, and light of the backlight, an external natural lightsource or an artificial light source can be all used, so powerconsumption can be reduced without being limited to the surroundingenvironments.

FIGS. 2A to 2F are cross-sectional views sequentially showing afabrication process of an array substrate of the general transflectiveLCD.

As shown in FIG. 2A, a gate electrode 21 made of a conductive materialis formed by using a photolithography process (a first masking process)on a substrate.

Next, as shown in 2B, a first insulation film 15 a, an amorphous siliconthin film and an n+ amorphous silicon thin film are sequentiallydeposited over the entire surface of the substrate 10 with the gateelectrode 21 formed thereon, and the amorphous silicon thin film and then+ amorphous silicon thin film are selectively patterned by using thephotolithography process (a second masking process) to form an activepattern 24 formed of the amorphous silicon thin film on the gateelectrode 21.

In this case, the n+ amorphous silicon thin film pattern 25 which hasbeen patterned in the same form as the active pattern 24 is formed onthe active pattern 24.

Thereafter, as shown in FIG. 2C, a conductive metal material isdeposited over the entire surface of the array substrate 10 and thenselectively patterned by using the photolithography process (a thirdmasking process) to form a source electrode 22 and a drain electrode 23at an upper portion of the active pattern 24. At this time, a certainportion of the n+ amorphous silicon thin film pattern formed on theactive pattern 24 is removed through the third masking process to forman ohmic-contact layer 25′ between the active pattern 24 and the sourceand drain electrodes 22 and 23.

Subsequently, as shown in FIG. 2D, a second insulation film 15 b,namely, an organic insulation film such as acryl, is deposited over theentire surface of the array substrate 10 with the source electrode 22and the drain electrode 23 formed thereon, and a portion of the secondinsulation film 15 b is removed through the photolithography process (afourth masking process) to form a contact hole 40 exposing a portion ofthe drain electrode 23.

In this case, as shown, the surface of the second insulation film 15 bis formed to be irregular (i.e., uneven, rough, jagged, bumpy,undulated, wavy, rippled, furrowed, ruffed, indented, serrated, etc.) toenhance reflection efficiency in the reflective mode.

As shown in FIG. 2E, a conductive metal material having goodreflectivity is deposited over the entire surface of the array substrate10 with the second insulation film 15 b formed thereon, and thenselectively patterned by using the photolithography process (a fifthmaking process) to form a reflective electrode 18 b electricallyconnected with the drain electrode 23 via the contact hole 40.

As shown in FIG. 2F, a transparent conductive metal material isdeposited over the entire surface of the array substrate 10, and then, apixel electrode 18 a is formed over the entirety of the pixel regionincluding a reflective part where the reflective electrode 18 b has beenformed, by using a photolithography process (a sixth masking process).

As mentioned above, in fabricating the array substrate including TFTs ofthe general transflective LCD, a total of six photolithography processesare necessarily performed. That is, the general transflective LCDrequires more photolithography processes compared to that of thetransmissive LCD.

The photolithography process is a process of transferring a patternformed on a mask onto the substrate on which a thin film is deposited toform a desired pattern, which includes a plurality of processes such asa process of coating a photosensitive solution, an exposing process anda developing process, etc., which, thus, degrades a production yield.

In particular, because the masks designed for forming the pattern arequite expensive, as the number of masks used in the processes increases,the fabrication cost of the LCD increases proportionally.

A technique for fabricating the array substrate by performing themasking process four times by forming the active pattern and the sourceand drain electrodes using a single masking process having a slit(diffraction) mask has been proposed.

However, because the active pattern, the source and drain electrodes andthe data lines are simultaneously patterned by performing an etchingprocess twice with the slit mask, the active pattern protrusivelyremains near the lower portions of the source electrode, the drainelectrode and the data lines.

The protrusively remaining active pattern is formed of an intrinsicamorphous silicon thin film, so the protrusively remaining activepattern is exposed to light from the lower backlight, generating anoptical current. The amorphous silicon thin film reacts slightly to ablinking of the light from the back light, and repeatedly becomesactivated and deactivated, which causes a change in the optical current.The changing optical current component is coupled with a signal flowingin the neighboring pixel electrodes so as to distort movement of theliquid crystal molecules positioned at the pixel electrodes. As aresult, a wavy noise is generated such that a wavy fine line appears ona screen of the LCD.

In addition, because the active pattern positioned at the lower portionof the data lines has portions that protrude at a certain height fromboth sides of the data lines, the opening region of the pixel part isencroached by as much as the protrusion height, thus resulting in areduction in an aperture ratio of the LCD.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the invention are directed to a liquidcrystal display (LCD) and its fabrication method that substantiallyobviate one or more of the problems due to limitations and disadvantagesof the related art.

An object of the embodiments of the invention is to provide atransflective liquid crystal display (LCD) and its fabrication methodcapable of fabricating an array substrate by performing a maskingprocess five times.

Another object of the embodiments of the invention is to provide atransflective LCD and its fabrication method capable of implementinghigh picture quality without generating a wavy noise.

Still another object of the embodiments of the invention is to provide atransflective LCD and its fabrication method capable of implementinghigh luminance by extending an opening region and solving an adhesionproblem between a pixel electrode formed of a transparent conductivefilm and an organic film.

Additional features and advantages of embodiments of the invention willbe set forth in the description which follows, and in part will beapparent from the description, or may be learned by practice ofembodiments of the invention. The objectives and other advantages of theembodiments of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimsthereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof embodiments of the invention, as embodied and broadly described, atransflective liquid crystal display (LCD) includes: a first substratedivided into a pixel part and first and second pad parts; a gateelectrode and a gate line formed at the pixel part of the firstsubstrate; a first insulation film formed on the first substrate; anactive pattern formed as an island at an upper portion of the gateelectrode and having a width smaller than the gate electrode; anohmic-contact layer and a barrier metal layer formed on the firstsubstrate and on source and drain regions of the active pattern; sourceand drain electrodes formed at the pixel part of the first substrate andelectrically connected with the source and drain regions of the activepattern via the ohmic-contact layer and the barrier metal layer; a dataline formed at the pixel part of the first substrate and crossing thegate line to define a pixel region including a reflective portion and atransmissive portion; a pixel electrode formed at the transmissiveportion of the pixel region and electrically connected with the drainelectrode; a source electrode pattern, a drain electrode pattern and adata line pattern formed at lower portions of the source electrode, thedrain electrode and the data line, and formed of a conductive film thatforms the pixel electrode; a reflective electrode formed at thereflective portion of the pixel region and electrically connected withthe drain electrode and the pixel electrode; a second insulation filmexposing the pixel electrode of the pixel region; and a second substrateattached to the first substrate in a facing manner.

To achieve these and other advantages and in accordance with the purposeof embodiments of the invention, as embodied and broadly described, amethod for fabricating a transflective LCD includes: providing a firstsubstrate divided into a pixel part and first and second pad parts;forming a gate electrode and a gate line at the pixel part of the firstsubstrate; forming a first insulation film on the first substrate;forming an active pattern as an island at an upper portion of the gateelectrode and forming an n+ amorphous silicon thin film pattern and aconductive film pattern on the active pattern; forming source and drainelectrodes at the pixel part of the first substrate and forming a dataline crossing the gate line to define a pixel region including areflective portion and a transmissive portion; forming a pixel electrodeformed of a transparent conductive film at the transmissive portion ofthe pixel region; forming a second insulation film on the firstsubstrate; forming a reflective electrode formed of an opaque conductivefilm at the reflective portion of the pixel region; and attaching thefirst and second substrates.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of embodiments as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the Drawings:

FIG. 1 is an exploded perspective view showing a general liquid crystaldisplay (LCD);

FIGS. 2A to 2F are cross-sectional views sequentially showing afabrication process of an array substrate of a general transflectiveLCD;

FIG. 3 is a plan view showing a portion of an array substrate of atransflective LCD according to the embodiment of the present invention;

FIGS. 4A to 4H are cross-sectional views sequentially showing afabrication process taken along lines IIIa-IIIa′, IIIb-IIIb andIIIc-IIIc of the array substrate in FIG. 3;

FIGS. 5A to 5E are plan views sequentially showing the fabricationprocess of the array substrate in FIG. 3; and

FIGS. 6A to 6F are cross-sectional views substantially showing a secondmasking process in FIGS. 4B and 5B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The transflective liquid crystal display (LCD) and its fabricationmethod will now be described in detail with reference to theaccompanying drawings.

FIG. 3 is a plan view showing a portion of an array substrate of thetransflective LCD according to the embodiment of the present invention,in which a single pixel including a gate pad part and a data pad partare shown for the sake of explanation.

Actually, the N number of gate lines and the M number of data lines areformed to cross each other to define the M×N number of pixels. Tosimplify the explanation, only a single pixel is shown.

As shown, gate lines 116 and the data lines are formed to be arrangedvertically and horizontally to define the pixel region on an arraysubstrate 110. A thin film transistor (TFT), a switching element, isformed at a crossing of the gate line 116 and the data line 117. A pixelelectrode 118 a and a reflective electrode 118 b are formed within thepixel region, is connected with the TFT to drive liquid crystal (notshown) together with a common electrode of a color filter substrate (notshown).

The pixel region refers to an image display region defined as the gateline 116 and the data line 117 cross, and includes a reflective portion(R) where the reflective electrode 118 b is formed to implement areflective mode and a transmissive portion (T) where the pixel electrode118 a is formed to implement a transmissive mode. Namely, with thereflective portion (R) and the transmissive portion (T) in the pixelregion, light made incident on from the exterior is reflected by thereflective electrode 118 b in the reflective mode so as to be emitted tothe exterior to display an image, and light emitting from a backlight istransmitted through the pixel electrode 118 a in the transmissive modeto display an image.

A gate pad electrode 126 p and a data pad electrode 127 p are formed atedge portions of the array substrate 110 and electrically connected withthe gate line 116 and the data line 117, and transfer a scan signal anda data signal applied from an external driving circuit unit (not shown)to the gate line 116 and the data line 117, respectively.

Namely, the gate line 116 and the data line 117 extend to the drivingcircuit unit so as to be connected with the corresponding gate pad line116 p and the data pad line 117 p, and the gate pad line 116 p and thedata pad line 117 p receive the scan signal and the data signal from adriving circuit unit through the gate pad electrode 126 p and the datapad electrode 127 p electrically connected with the gate pad line 116 pand the data pad line 117 p. Herein, reference numeral 140 denotes agate pad part contact hole, and the gate pad electrode 126 p iselectrically connected with the gate pad line 117 p via the gate padpart contact hole 140.

The TFT includes a gate electrode 121 connected with the gate line 116,a source electrode 122 connected with the data line 117, and a drainelectrode 123 connected with the pixel electrode 118 a and thereflective electrode 118 b. The TFT also includes an active pattern 124for forming a conductive channel between the source and drain electrodes122 and 123 by a gate voltage supplied to the gate electrode 121.

In the embodiment of the present invention, the active pattern 124 isformed of an amorphous silicon thin film, and is formed as an island atan upper portion of the gate electrode 121 to thus reduce an off currentof the TFT.

At a lower portion of the source electrode 122, the drain electrode 123and the data line 117 made of an opaque conductive material, there areformed a source electrode pattern (not shown), a drain electrode pattern(not shown) and a data line pattern (not shown) made of a transparentconductive material and patterned in the same form as the sourceelectrode 122, the drain electrode 123 and the data line 117.

Although not shown in detail, the reflective electrode 118 b formed ofan opaque conductive film is formed on a second insulation film formedof an organic film and having a bumpy surface.

In the embodiment of the present invention, because the pixel electrode118 a, the source electrode pattern, the drain electrode pattern and thedata line pattern formed of a transparent conductive film are formedbelow the source electrode, the drain electrode 123 and the data line117, and the second insulation firm is formed above the source electrode122, the drain electrode 123 and the data line 117, so there is noadhesion problem between the second insulation film and the transparentconductive film. Namely, there is an adhesion problem between the secondinsulation film formed of the organic film and the transparentconductive film made of ITO or IZO, so plasma processing should benecessarily performed in forming the second insulation film having thebumpy surface. But in the embodiment of the present invention, becausethe pixel electrode 118 a, the source electrode pattern, the drainelectrode pattern and the data line pattern, which are formed of thetransparent conductive film, are formed below the source electrode 122,the drain electrode 123, and the data line 117, so the adhesion problembetween the second insulation film and the transparent conductive filmcan be basically avoided.

A portion of the source electrode 122 extends in one direction to form aportion of the data line 117, and a portion of the drain electrodepattern extends to the pixel region to form the pixel electrode 118.

A portion of the previous gate line 116′ overlaps with a portion of thepixel electrode 118 with a first insulation film (not shown) interposedtherebetween to form a storage capacitor Cst. The storage capacitor Cstserves to uniformly maintain voltage applied to a liquid crystalcapacitor until a next signal is received. Namely, the pixel electrode118 of the array substrate 110 forms the liquid crystal capacitortogether with the common electrode of the color filter substrate, and ingeneral, voltage applied to the liquid crystal capacitor is notmaintained until the next signal is received but leaked. Thus, in orderto uniformly maintain the applied voltage, the storage capacitor Cstshould be connected with the liquid crystal capacitor.

Besides maintaining the signal, the storage capacitor may also have theeffect of stabilizing a gray scale display, reducing flickering effects,reducing the formation of residual images, and the like.

In the LCD according to the embodiment of the present invention, thesource and drain electrodes 122 and 123, the pixel electrode 118 and thepad part electrodes 126 p and 127 p are patterned and also the pixelregion and the pad part form an opening using a single mask such thatthe array substrate 110 can be fabricated by performing the maskingprocess a total of fifth times using four masks. The fabrication methodof the LCD will now be described as follows.

FIGS. 4A to 4H are cross-sectional views sequentially showing afabrication process taken along lines IIIa-IIIa′, IIIb-IIIb′ andIIIc-IIIc′ of the array substrate in FIG. 3. The left side shows theprocess of fabricating the array substrate of the pixel part and theright side shows the sequential process of fabricating the arraysubstrate of the data pad part and the gate pad part.

FIGS. 5A to 5E are plan views sequentially showing the fabricationprocess of the array substrate in FIG. 3.

As shown in FIGS. 4A and 5A, the gate electrode 121 and gate lines 116and 116′ on the pixel part of the array substrate 110 made of atransparent insulation material such as glass, and the gate pad line 116p is formed on the gate pad part of the array substrate 110.

Reference numeral 116′ refers to the previous gate line with respect toa corresponding pixel, and the gate line 116 of the corresponding pixeland the previous gate line 116′ are formed in the same manner.

In this case, the gate electrode 121, the gate lines 116 and 116′ andthe gate pad line 116 p are formed by depositing a first conductive filmover the entire surface of the array substrate 110 and selectivelypatterning it through the photolithography process (the first maskingprocess).

Herein, the first conductive film can be made of a low-resistance opaqueconductive material such as aluminum (Al), an aluminum alloy, tungsten(W), copper (Cu), chromium (Cr) and molybdenum (Mo), and the like. Also,the first conductive film can be formed with a multi-layered structureby stacking two or more low-resistance conductive materials.

Next, as shown in FIGS. 4B and 5B, a first insulation film 115 a, anamorphous silicon thin film, an n+ amorphous silicon thin film and asecond conductive film are formed over the entire surface of the arraysubstrate 110 of the array substrate 110 with the gate electrode 121,the gate lines 116 and 116′ and the gate pad line 116 p formed thereon,and then selectively removed through the photolithography process (asecond masking process) to form an active pattern 124 formed of theamorphous silicon thin film at an upper portion of the gate electrode121 and at the same time to form a gate pad part contact hole 140exposing a portion of the gate pad line 116 p.

An n+ amorphous silicon thin film pattern 125′ and a conductive filmpattern 130′, which are formed of the n+ amorphous silicon thin film andthe second conductive film and have the same pattern as the activepattern 124, remain on the active pattern 124.

In the embodiment of the present invention, the gate pad part contacthole 140 is formed long in a direction substantially parallel to thegate pad line 116 p. However, the present invention can be applicableregardless of the configuration of the gate pad part contact hole 140.

Herein, in the embodiment of the present invention, the active pattern124 is formed as an island over the gate electrode 121 and within theboundaries defined by the perimeter of the gate electrode 121 with thefirst insulation film 115 a interposed therebetween, and the activepattern 124 and the gate pad part contact hole 140 are formed using asingle mask, such as a half-tone mask or a diffraction (slit) mask(hereinafter, it is assumed that referring to the half-tone mask meansit also includes the diffraction mask). The second masking process willnow be described in detail as follows.

FIGS. 6A to 6F are cross-sectional views showing a second maskingprocess in detail in FIGS. 4B and 5B.

As shown in FIG. 6A, the first insulation film 115 a, the amorphoussilicon thin film 120, the n+ amorphous silicon thin film 125 and thesecond conductive film 130 are formed over the entire surface of thearray substrate 110 with the gate electrode 121, the gate lines 116 and116′ and the gate pad line 116 p formed thereon.

In this case, the second conductive film 130 is used as a barrier metallayer that reduces contact resistance between an ohmic-contact layerformed on the n+ amorphous silicon thin film and source/drain electrodepatterns formed of a transparent conductive film (to be described), andcan be formed with a thickness of about 50 Å-100 Å by using a conductivematerial such as molybdenum.

Thereafter, as shown in FIG. 6B, a first photosensitive film 170 made ofa photosensitive material such as photoresist is formed over the entiresurface of the array substrate 110, on which light is selectivelyirradiated through the half-tone mask 180.

The half-tone mask 180 used in the embodiment of the present inventionincludes a first transmission region (I) that allows irradiated light tobe entirely transmitted therethrough, a second transmission region (II)that allows only light to be partially transmitted therethrough whileblocking the remaining light, and a blocking region (III) that entirelyblocks the irradiated light. Only light which has transmitted throughthe half-tone mask 180 can be irradiated onto the first photosensitivefilm 170.

Subsequently, when the first photosensitive film 170 which has beenexposed through the half-tone mask 180 is developed, as shown in FIG.6C, first and second photosensitive film patterns 170 a and 170 b remainat regions where light has been entirely blocked or partially blockedthrough the blocking region (III) and the second transmission region(II), and the first photosensitive film at the transmission region (I)through which light had been entirely transmitted has been completelyremoved to expose the surface of the second conductive film 130.

At this time, the first photosensitive film pattern 170 a formed at theblocking region III is thicker than the second photosensitive filmpattern 170 b formed through the second transmission region II. Inaddition, the photosensitive film at the region where the light hadentirely transmitted through the first transmission region I has beencompletely removed. This is because positive photoresist has been used.However, negative photoresist can be also used in the embodiments of thepresent invention.

Thereafter, as shown in FIG. 6D, the first insulation film 115 a, theamorphous silicon thin film 120, the n+ amorphous silicon thin film 125and the second conductive film 130 are selectively removed by using thefirst and second photosensitive film patterns 170 a and 170 b as masksto form the gate pad part contact hole 140 exposing a portion of thegate pad line 116 p at the gate pad part of the array substrate 110.

Then, an ashing process is performed to remove a portion of the firstphotosensitive film pattern 170 a and the entirety of the secondphotosensitive film pattern 170 b. Then, as shown in FIG. 6E, the secondphotosensitive film pattern of the second transmission region II iscompletely removed.

In this case, the first photosensitive film pattern remains as a thirdphotosensitive film pattern 170′ by removing the thickness of the secondphotosensitive film pattern only at the active pattern regioncorresponding to the blocking region III.

Thereafter, as shown in FIG. 6F, portions of the amorphous silicon thinfilm, the n+ amorphous silicon thin film and the second conductive filmare removed by using the remaining third photosensitive film pattern170′ as a mask to form the active pattern 124 as an island over the gateelectrode 121 and within boundaries defined by the perimeter of the gateelectrode 121 to thus reduce an off current of the TFT.

At this time, the n+ amorphous silicon thin film pattern 125′ and theconductive film pattern 130′, which are formed of the n+ amorphoussilicon thin film and the second conductive film and have been patternedin the same form as the active pattern 124, remain at the upper portionof the active pattern 124.

In the embodiment of the present invention, the active pattern 124 isformed as an island over the gate electrode 121 and within boundariesdefined by the perimeter of the gate electrode 121 to thus reduce an offcurrent of the TFT.

Next, as shown in FIGS. 4C and 4D, third and fourth conductive films 150and 160 are deposited over the entire surface of the array substrate 110with the active pattern 124 formed thereon.

A second photosensitive film 270, which has been patterned to have acertain form, is formed on the array substrate 110 (a third maskingprocess).

Thereafter, as shown in FIGS. 4E and 5C, portions of the third andfourth conductive films 150 and 160 are removed by using the secondphotosensitive film 270 as a mask to form the pixel electrode 118 formedof the third conductive film and at the same time to form the sourceelectrode 122, the drain electrode 123 and the data line 117 formed ofthe fourth conductive film at the pixel part of the array substrate 110.

In addition, through the third masking process, the data pad electrode127 p and the gate pad electrode 126 p, which are formed of the thirdconductive film, are formed at the data pad part and the gate pad partof the array substrate 110.

In this case, on the lower part of the source electrode 122, the drainelectrode 123 and the data line 117, there are formed a source electrodepattern 122′, a drain electrode pattern 123′ and a data line pattern(not shown) are formed from the third conductive film and patternedaccording to the shape of the source electrode 122, the drain electrode123 and the data line 117.

In addition, a pixel electrode pattern 160′, a data pad electrodepattern 160″ and a gate pad electrode pattern 160′″ formed of a fourthconductive film and patterned according to the shape of the pixelelectrode 118, the data pad electrode 127 p and the gate pad electrode126 p remain at the upper portions of the pixel electrode 118, the datapad electrode 127 p and the gate pad electrode 126 p.

A certain region of the n+ amorphous silicon thin film pattern 125′formed on the active pattern 124 is removed through the third maskingprocess to form an ohmic-contact layer 125″ that allows the activepattern 124 and the source and drain electrodes 122 and 123 toohmic-contact with each other, and a barrier metal layer 130″ made ofthe second conductive film and patterned in the same form as theohmic-contact layer 125″ is formed at the upper portion of theohmic-contact layer 125″.

In this case, the gate pad electrode 126 p is electrically connectedwith the lower gate pad line 116 p via the gate pad part contact hole140, and the pixel electrode 118 is connected with the drain electrodepattern 123′ so as to be electrically connected with the drain electrode123.

Herein, the third conductive film is made of a transparent conductivematerial with good transmittance such as indium-tin-oxide (ITO) orindium-zinc-oxide (IZO) to form the pixel electrode 118, the data padelectrode 127 p and the gate pad electrode 126 p. The fourth conductivefilm can be made of low-resistance opaque conductive material such asaluminum (Al), an aluminum alloy, tungsten (W), copper (Cu), chromium(Cr) and molybdenum (Mo), or the like to form the source electrode 122,the drain electrode 123 and the data line.

In the embodiment of the present invention, a tail of the active patternformed of the amorphous silicon thin film does not exist at the lowerportion of the data line 117, so there is no signal interference of thedata line 117 possible by the tail and an aperture ratio increases bythe width of the tail of the active pattern. In addition, because thereis no tail of the active pattern, no wavy noise is generated, and thus,the LCD can have high picture quality. For reference, as mentionedabove, the tail of active pattern is formed at the lower portion of thedata line during the process of forming the active pattern, the sourceand drain electrodes and the data line by using the slit mask throughthe single making process, and because it has width wider than that ofthe data line, it causes the signal interference of the data line anddegradation of an aperture ratio.

As shown in FIGS. 4F, 4G and 5D, the second insulation film 115 b and athird photosensitive film 370, which has been patterned to have acertain form, are formed over the entire surface of the array substrate110 and then the second insulation film 115 b is selectively removed byusing the photolithography process (a fourth masking process) to openthe pixel region and the pad part. In this case, the second insulationfilm 115 b may be formed of an organic film such as photoacryl to have abumpy surface at the reflective portion. The bumpy surface serves toincrease reflectivity of the reflective portion.

In this case, as mentioned above, because the pixel electrode 118 a, thesource electrode pattern 122′, the drain electrode pattern 123′, and thedata line pattern 117′, which are formed of the transparent conductivefilm, are formed underneath the source electrode 122, the drainelectrode 123, and the data line 117, and the second insulation film 115b is formed on the source electrode 122 and the drain electrode 123, sothe adhesion problem can be avoided between the second insulation film115 b and the transparent conductive films (namely, the pixel electrode118 a, the source electrode pattern 122′, the drain electrode pattern123′, and the data line pattern 117′).

The pixel electrode pattern 160′, the data pad electrode pattern 160″and the gate pad electrode pattern 160′″ are removed by using the fourthmasking process to expose the pixel electrode 118, the data padelectrode 127 p and the gate pad electrode 126 p. A portion of thecorresponding pixel electrode 118 overlaps with a portion of theprevious gate line 116′ to form a storage capacitor Cst together withthe previous gate line 116′ with the first insulation film 115 ainterposed therebetween.

Thereafter, as shown in FIGS. 4H and 5E, a fifth conductive film isformed over the entire surface of the array substrate 110 andselectively removed by using the photolithography process (a fifthmasking process) to form the reflective electrode 118 b at thereflective portion.

The fifth conductive film may be made of a conductive material with goodreflectivity such as aluminum to form the reflective electrode 118 b.

The array substrate according to the embodiment of the present inventionis attached with color filter substrates in a facing manner by a sealantapplied to outer edges of the image display part. In this case, thecolor filter substrates include black matrixes for preventing leakage oflight to the TFTs, the gate lines and the data lines and color filtersfor implementing red, green and blue colors.

The attachment of the color filter substrates and the array substratesare made through attachment keys formed on the color filter substratesor the array substrates.

In the embodiment of the present invention, as the active patterns, theamorphous silicon TFT using the amorphous silicon thin film is used asan example, but the present invention is not limited thereto and as theactive patterns, polycrystalline silicon TFTs using a polycrystallinesilicon thin film can be also used.

The present invention can be also applied to a different display devicefabricated by using TFTs, for example, an OLED (Organic Light EmittingDiode) display device in which OLEDs are connected with drivingtransistors.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalents of such metes and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. A transflective liquid crystal display devicecomprising: a first substrate divided into a pixel part and first andsecond pad parts; a gate electrode and a gate line formed of a firstconductive film at the pixel part of the first substrate; a firstinsulation film formed on the first substrate with the gate electrodeand a gate line formed thereon; an active pattern formed as an island atan upper portion of the gate electrode, wherein the active pattern isflat owing to having a width smaller than the gate electrode; a flattype of an ohmic-contact layer formed of an n+ amorphous silicon thinfilm on the active pattern; a flat type of a barrier metal layer formedof a second conductive film at an upper portion of the ohmic-contactlayer, wherein the barrier metal layer is a single layer, issubstantially patterned in the same size as the ohmic-contact layer andan entire lower portion of the barrier metal layer contacts with theohmic-contact layer; source and drain electrodes formed of a fourthconductive film over the barrier metal layer and electrically connectedwith source and drain regions of the active pattern via theohmic-contact layer and the barrier metal layer; a data line formed atthe pixel part of the first substrate and crossing the gate line todefine a pixel region including a reflective portion and a transmissiveportion; a pixel electrode formed of a third conductive film at thetransmissive portion of the pixel region and electrically connected withthe drain electrode; a source electrode pattern, a drain electrodepattern and a data line pattern formed of the third conductive film atlower portions of the source electrode, the drain electrode and the dataline, respectively, wherein the barrier metal layer reduces contactresistance between the ohmic-contact layer and the source/drainelectrode patterns and wherein an entire upper portion of the barriermetal layer contacts with the source/drain electrode patterns; a secondinsulation film exposing the pixel electrode of the pixel region on thefirst substrate with the source and drain electrodes formed thereon; areflective electrode formed of a fifth conductive film at the reflectiveportion of the pixel region and electrically connected with the drainelectrode and the pixel electrode; and a second substrate attached tothe first substrate in a facing manner.
 2. The device of claim 1,further comprising: a gate pad line formed at the first pad part of thefirst substrate.
 3. The device of claim 2, further comprising: a contacthole formed by removing a portion of the first insulation film, andexposing a portion of the gate pad line.
 4. The device of claim 3,further comprising: a gate pad electrode electrically connected with thegate pad line via the contact hole.
 5. The device of claim 1, whereinthe second conductive film is made of a low resistance conductivematerial such as molybdenum.
 6. The device of claim 1, wherein thesecond conductive film has a thickness of about 50 Å to 100 Å.
 7. Thedevice of claim 1, wherein the source electrode pattern, the drainelectrode pattern and the data line pattern are patterned in the sameform as the source electrode, the drain electrode, and the data line. 8.The device of claim 1, further comprising: a data pad line formed at thesecond pad part of the first substrate.
 9. The device of claim 8,further comprising: a data pad electrode formed at the second pad partof the first substrate and electrically connected with the data padline.
 10. The device of claim 1, wherein a portion of the secondinsulation film is removed to expose the pixel electrode of the pixelregion.
 11. The device of claim 1, wherein the second insulation film isformed to have a bumpy surface.
 12. The device of claim 1, wherein thesecond insulation film is made of an organic film such as photoacryl.